Convulsion Risk From CSL Flu Vaccine Linked to Components

By Jason Gale -
Jun 20, 2012

Convulsions in children immunized
with a CSL Ltd. (CSL) flu shot probably were caused by an excessive
immune response to viral components in the vaccine, according to
preliminary findings of a two-year study.

Use in children younger than 6 years of CSL’s Fluvax
vaccine, to protect against the three main influenza strains
circulating in the 2010 Southern Hemisphere winter, was
suspended by Australian health officials in April of that year.
Doctors reported a nine-fold increase in fever and convulsions
in children following immunization with Fluvax.

CSL, the Southern Hemisphere’s only flu-vaccine maker,
hasn’t been able to license Fluvax for use in young children
since the complications were noted. An investigation into the
cause indicated CSL’s manufacturing method preserves more short-
gene fragments and lipids from the virus than other makers, the
Melbourne-based company said today.

“While influenza vaccines must contain virus components to
stimulate sufficient protection against influenza, it appears
that components of the inactivated virus retained in Fluvax in
2010 overstimulated the developing immune systems of some young
children compared to previous seasons,” Darryl Maher, vice
president of medical and research at CSL’s biotherapies
division, said in a statement.

CSL declined 1.2 percent to A$38.85 at the close of trading
on the Australian stock exchange, paring to 21 percent the
stock’s gain this year.

Investigation’s Results

The findings were drawn from an investigation monitored by
Australia’s drugs regulator. Results of the investigation were
presented at an immunization meeting in Darwin today.

Fever-induced seizures in children vaccinated with Fluvax
were observed at a rate of five to seven cases of per 1,000
doses, compared with an incidence of febrile convulsions of 0.08
to 0.17 with other flu vaccines, Australia’s Therapeutic Goods
Administration said in a 2010 report.

Vaccination with Fluvax vaccine in 2010 may have caused two
to three hospital admissions for febrile convulsions for every
flu-related admission it prevented, doctors from Melbourne and
Perth wrote in a 2010 study.

Particular characteristics of gene fragments or lipids from
two of the flu strains used in the 2010 Fluvax may have led it
to being more reactive in some young children compared with CSL
vaccines used in previous seasons, the company said today.
Inactivated whole virus and clusters of pieces of virus split by
a chemical process may have contributed, and are under
investigation.

Fluvax isn’t licensed in Australia for use in children
under 5 years and is only recommended for at-risk children ages
5 to 9 years if no other licensed influenza vaccine is
available.

CSL is working to better understand the cause of the
adverse events and identify potential manufacturing-process
changes that will prevent them from happening again, it said.

“Until these further studies are completed, and both CSL
and the regulators are fully confident that our manufacturing
process can consistently produce a safe and effective influenza
vaccine for children, we will continue to fully support the age
restrictions currently in place for children in all markets,”
Maher said.